Connection type carbon electrode

ABSTRACT

A connectable carbon electrode having a coaxial projecting portion and a coaxial socket portion for connecting a plurality of the electrodes in succession in which a plurality of elongated indentations are provided on the projecting portion along a predetermined length thereof. This enables the projecting portion to be securely fitted into the inner wall of the socket portion by scrapping off the indentations by the inner wall of the socket portion.

United States Patent [1 1 Matsuo et a1.

[ Mar. 12, 1974 CONNECTION TYPE CARBON ELECTRODE [75] Inventors: KojiroMatsuo; Fukutaro Mizukami;

Koshi Ishihara; Masanori Maeda; Hideo Ishii, all of Osaka, Japan [30]Foreign Application Priority Data Dec. 27, 1971 Japan 47-1715 [52] US.Cl 219/145, 13/18, 219/119, 219/136, 313/354, 313/355, 313/357 [51] Int.Cl B23k 35/00 [58] Field of Search ..2l9/l19, 136,145,146; 313/355, 357,354; 287/2; 285/3321; 13/18 3,074,292 l/1963 Polmon 287/2 3,030,5444/1962 Zamboldi et al..... 313/355 3,621,187 11/1911 Reichelt 219/1453,399,322 8/1965 Ambe 219/145 3,373,308 3/1968 Perrin 313/357 PrimaryExaminer-Bruce A. Reynolds Assistant Examiner-George A. Montanye [5 7]ABSTRACT A connectable carbon electrode having a coaxial projectingportion and a coaxial socket portion for connecting a plurality of theelectrodes in succession in which a plurality of elongated indentationsare provided on the projecting portion along a predetermined lengththereof. This enables the projecting portion to be securely fitted intothe inner wall of the socket portion by scrapping off the indentationsby the inner wall of the socket portion.

3 Claims, 10 Drawing Figures [5 6] References Cited UNITED STATESPATENTS 3,633,063 l/1972 Ando 219/145 1 CONNECTION TYPE CARBON ELECTRODEThe present invention relates to a connectable type carbon electrode andmore particularly to a carbon electrode capable of firmly connecting thetwo electrodes having substantially a coaxial projecting portion and acoaxial socket portion, respectively as well as enabling the electrodesto contact each other in a good conductive condition.

In a carbon electrode which is used in the gouging and blasting work bythe are air method, it is necessary that the electrode have a smallerresistance and that the oxidative wear be reduced in order to obtainstability of the arc condition since a large electric current must passtherethrough. For this reason, a conductive metal such as a coppermaterial is coated on the surface of the carbon electrode. In the workdescribed above, shaving, cutting, perforation, or trimming areperformed by arc heat which is produced by splashing the arc currentbetween the carbon electrode and a work piece metal as well as byblowing the melted metal through jet air. Therefore, the length of thecarbon electrode is reduced during the job in proportion to the amountof the work done.

Accordingly, it is necessary to change the carbon electrode one by oneat the time of consumption of the carbon electrode during the progressof the job. However, when the carbon electrode is changed during thejob, the shape of the object to ge gouged, for instance, tends to bevaried. Also one end portion of the carbon electrode remains unused, sothat it is waste. In the conventional carbon electrodes with a coaxialprojection and coaxial socket portion such as shown in FIGS. 1 and 2, aconductive metal 4' is coated only on the body 1' of the carbonelectrode. However, in this con struction, a favorable contact conditioncan not be obtained between the projecting portion 2' and socket portion3', so that the contact condition of the two portions is affected by thevariations in structural features of each carbon rod. As a result, thecontact resistance tends to increase, or becomes large, so that theconnecting portion is heated during operation and the coated conductivemetal tends to be melted. As a result of this, the base of the carbon isexposed and oxidized, so that it is not possible for the carbonelectrode to fully function as an electrode because of collapse andbreakage.

An object of the present invention, therefore, is to provide aconnectable carbon electrode capable of maintaining a good electricalcontact between the coaxial projecting portion of one electrode and thecoaxial socket portion of the other electrode.

A further object of the present invention is to provide a connectabletype carbon electrode which has a small contact resistance and is notliable to misconnection due to the heat generated in a contactedportion.

A still further object of the present invention is to provide aconnectable type carbon electrode in which an conductive metal coatingis provided up to indentations of the projecting portion and alsoslightly to the inner portion of the socket portion.

A still further object of the present invention is to provide aconnectable carbon electrode capable of being easily manipulated duringwork.

These and other objects and advantages of the present invention will beapparent from the following description and accompanying drawings inwhich:

FIG. 1 shows a connectable carbon electrode according to the prior art;

FIG. 2 shows another carbon electrode according to the prior art;

FIG. 3 a shows an embodiment according to the present invention in whichan internal construction is partly shown by a broken window;

FIG. 3 b shows both end views of the electrode of FIG. 3 a;

FIG. 4 shows an enlarged projecting portion of the embodiment of FIG. 3a;

FIG. 5 shows an enlarged socket portion of the embodiment of FIG. 3(a).

FIG. 6 shows a cross sectional view of the embodiment according to thepresent invention in a connected condition;

FIG. 7 shows a cross sectional view of FIG. 6 cut by AA section; v

FIG. 8 shows an another embodiment according to the present invention inwhich no taper is provided on the convex portion; and

FIG. 9 shows a cross sectional view of the embodiment of FIG. 8 which isin the socket portion of the another electrode of the same type.

A carbon electrode according to the present invention is made of amixture of 90 parts by weight of synthetic graphite, 10 parts by weightof carbon black, parts by weight of binder composed of tar and pitch,and the mixture is then kneaded in a high temperature atmosphere and isthrust from a suitable machine and then is cut in a predetermined size.The calcined carbon is then cooked in a reduction atmosphere and isfinally graphitized.

In order to electroplate the carbon electrode thus made, copper sulfatel60-200g, and a sulfaric acid of 40-60g are added to one liter of waterand the carbon electrode is immersed in the electrolytic bath with thesocket portion downward. In this case, the current density willpreferable be 3-5A/cm The socket portion is immersed to the boundarybetween a large diameter portion and a small diameter portion thereof,while the projecting portion is immersed in the electrolytic bath up tothe indentations.

Referring now to FIGS. 3 through 5, a connectable carbon electrodeaccording to the present invention is shown. The carbon electrode 1 hasa coaxial projecting portion 2 and a coaxial socket portion 3,respectively. There is provided on the projecting portion 2 a pluralityof elongated indentations 4. Also, the carbon electrode is coated with aconductive metal 5 which is extended to the beginning of theindentations 4 along the tapered portion 6. The other end of theindentation thereof has also a tapered portion 7 forming an inlet whichis steeper than that of the portion 6. For instance, the portion 6 has atapered degree of about 1 to 8 and the portion 7 has a tapered degree ofabout to The length of the tapered portion 6 and that of the indentedportion are nearly same.

The plurality of the indentations are substantially in the form ofelongated grooves and are preferably about 1mm in depth. These elongatedindentations are formed by knurling. On the other hand, the socketportion 3 of the carbon electrode 1 is formed in such a way that theprojecting portion 2 of the other electrode can be inserted therein.Namely, the socket portion 3 has two sections 8 and 9. The diameter ofthe section 9 is larger than that of section 8 and the length of thesocket portion consisting of the sections 8 and 9 is slightly longerthan that of the projecting portion 2. The diameter of the section 8 isslightly smaller than that of the indented portion, say, by about0.05-0.5mm, so that when the projecting portion 2 is inserted into thesocket portion 3, the portion with the elongated indentations 4, ispartly scraped off by the inner wall of the section 8. The diameter ofthe section 9 is larger than that of the section 8 within 3mm, and it isalso larger than the maximum diameter of the tapered portion 6 by about2mm.

Now, reference is made to FIGS. 6 and 7. When connecting, the projectingportion 2 is forced into the socket portion 3 of the other carbonelectrode 11, so that at the time of insertion, the indentations 4 arescraped off by the inner wall of the socket section 8. Accordingly, agood connection and contact is obtained not only at the indented portionarea 1 l, but also at the tapered portions 12 of the projecting portionand socket portion respectively. This means that the contact resistanceof the carbon electrodes is very small, so that red-heated conditionencountered in the prior art is avoided and the possibility ofmalconnection and disconnection will also be remarkably reduced. Inaddition, since the indented portion of the projecting portion is forcedto be inserted into the socket portion of the other electrode, noadditional support member is required when connecting the two electrodes1 and 1. FIG. 7 shows a cross sectional view of the portion cut by A-Asection. In FIG. 8, an another embodiment of the present invention isshown, wherein the same numerals corresponding to FIG. 3 are used. Inthe carbon electrode in this embodiment, no tapered portion is providedon the projecting portion, so that the diameter of the indented portion4 and that of the section 6 are nearly the same.

However, the length of the indented portion is fairly longer than thatof the untapered portion 6, so that the length of section 8 is longerthan that of section 9, accordingly.

There is no difference with respect to the remaining portions of theelectrode.

FIG, 9 shows the two electrodes in a connected condition, wherein thesame numerals are used.

Though preferred embodiments of the present invention have been shownand described in the foregoing, it is to be understood that this hasbeen done merely by way of example and not with the object of limitingthe 4 spirit of the present invention.

What is claimed is:

l. A connectable carbon electrode comprising an electrode body of carboncoated on its outer periphery with a thin copper layer, a coaxialprojecting portion of carbon material provided on one end of said bodyand coated on its peripheral surface along a predetermined length with aslightly tapered thin copper layer, which is continuous with the copperlayer on the outer periphery of the electrode body, a remaining part ofsaid predetermined length of the projecting portion being provided withelongated indentations of carbon, a coaxial socket portion of carbonmaterial provided inside the other end of said body and having an innerwall surface defining the socket in a substantially similar shape tosaid projecting portion, said socket being coated with a thin taperedcopper layer along a predetermined length of the inner wall, which iscontinuous with the thin copper layer on the outer periphery of theelectrode body and which extends inwardly from the open end of thesocket in a first section thereof, the socket having a second sectioninwardly of said first section and with an inner diameter smaller thanthe inner diameter of said first section, the inner diameter of saidsecond section being smaller than the outer diameter of the remainingpart having said elongated indentations and the inner diameter of saidfirst section is larger than the largest outer diameter of saidprojecting portion of carbon material, whereby when a projecting portionof a connectable carbon electrode is inserted into a socket portion of acorresponding electrode the remaining part of said projecting portionhaving the indentations is tightly received in said second section ofsaid socket as the carbon is partially scraped off the remaining partalong the walls of said second section during insertion, and saidslightly tapered thin copper layer on said projecting portion is wedgedinto tight engagement with the thin tapered copper layer in said firstsection of said socket so as to provide a good electrical and a strongmechanical connection between the electrodes.

2. A connectable carbon electrode according to claim 1, wherein saidperipheral surface of the predetermined length of said projectingportion is tapered from the electrode body.

3. A connectable carbon electrode according to claim 1, wherein thediameter of the predetermined length of said projecting portion and thediameter of said remaining part are approximately the same.

1. A connectable carbon electrode comprising an electrode body of carboncoated on its outer periphery with a thin copper layer, a coaxialprojecting portion of carbon material provided on one end of said bodyand coated on its peripheral surface along a predetermined length with aslightly tapered thin copper layer, which is continuous with the copperlayer on the outer periphery of the electrode body, a remaining part ofsaid predetermined length of the projecting portion being provided withelongated indentations of carbon, a coaxial socket portion of carbonmaterial provided inside the other end of said body and having an innerwall surface defining the socket in a substantially similar shape tosaid projecting portion, said socket being coated with a thin taperedcopper layer along a predetermined length of the inner wall, which iscontinuous with the thin copper layer on the outer periphery of theelectrode body and which extends inwardly from the open end of thesocket in a first section thereof, the socket having a second sectioninwardly of said first section and with an inner diameter smaller thanthe inner diameter of said first section, the inner diameter of saidsecond section being smaller than the outer diameter of the remainingpart having said elongated indentations and the inner diameter of saidfirst section is larger than the largest outer diameter of saidprojectinG portion of carbon material, whereby when a projecting portionof a connectable carbon electrode is inserted into a socket portion of acorresponding electrode the remaining part of said projecting portionhaving the indentations is tightly received in said second section ofsaid socket as the carbon is partially scraped off the remaining partalong the walls of said second section during insertion, and saidslightly tapered thin copper layer on said projecting portion is wedgedinto tight engagement with the thin tapered copper layer in said firstsection of said socket so as to provide a good electrical and a strongmechanical connection between the electrodes.
 2. A connectable carbonelectrode according to claim 1, wherein said peripheral surface of thepredetermined length of said projecting portion is tapered from theelectrode body.
 3. A connectable carbon electrode according to claim 1,wherein the diameter of the predetermined length of said projectingportion and the diameter of said remaining part are approximately thesame.